Suicide is the 2nd leading cause of death among youth ages 12 to 17 in the United States. However, most youth at high risk for suicide go unrecognized and untreated, and for half of adolescent suicides, the first suicide attempt is fatal To improve identification of youth at risk for suicide, in response to RFA-MH-14-070, Pediatric Suicide Prevention in Emergency Departments, we propose a multi-site collaborative project with the Pediatric Emergency Care Applied Research Network (PECARN) and the Whiteriver PHS Indian Hospital. These EDs serve geographically and socio-demographically diverse groups of youth, including American Indian youth who are at particularly high risk for suicide. In Study 1, we will implement a universal suicide risk assessment using a broad range of risk factors with 6743 youth, ages 12 to 17 years, who present to one of 14 emergency departments (EDs) during randomly chosen screening shifts. We will follow-up a subsample of 30% of these youth, enriched for suicide risk factors, at 3 and 6 months. Our specific aims are to: (1) develop a computerized adaptive screen (CAS) for predicting suicide attempts; (2) compare the psychometric properties (e.g., sensitivity, specificity) of the CAS to those of a standard screen, the Ask Suicide-Screening Questions (ASQ); (3) test the ability of the Implicit Association Test (IAT), a behavioral test of implicit suicidal cognitions, to add incrementally to the prediction of suicide attempts above and beyond screening scores; and (4) develop and validate a parsimonious CAS-based algorithm for risk stratification to facilitate the triage of youths. In Study 2, we will recruit a new sample of 2340 youth (stratified by suicide risk factors), administe the CAS and ASQ, and follow-up youth at 3-months with interviews and medical chart reviews. Our Study 2 aim is to validate the specificity and sensitivity of the CAS and ASQ for predicting suicide attempts. The optimal screen developed in this collaborative project will have the potential to be disseminated nationwide to enhance the capacity of emergency departments to identify and effectively triage youth at acute risk for suicide attempts. This project is significat because the screening and triage of at-risk youth in healthcare settings are key strategies of the National Strategy for Suicide Prevention to reduce adolescent suicide. It is highly innovative because it will develop and test a computerized adaptive screen (CAS), which results in individualized sequences of screening questions conditional on previous responses; and it will test a wide range of acute suicide risk indicators for possible inclusion in the CAS. In addition, this project will test the incremental value of the IAT, which is important as many at-risk youth may deny suicidal thoughts. This project is feasible given PECARN's strong infrastructure and record of successful recruitment, and the investigative team's collective experience in multi-site studies, computerized adaptive testing, and youth suicide research in ED settings.